EF 6，Code First Database表未创建

Question

我有群组用户类：

    [Table("tblGroupUser")]
    public class UserGroup : MyTemplate
    {
        public UserGroup()
        {
            Users = new List<User>();
        }

        [Key]
        [DisplayName("Group Code"), Column("GroupCode", TypeName = "varchar")]
        [MaxLength(20, ErrorMessage = "Group Code maximum length is {0}")]
        [Required(AllowEmptyStrings = false, ErrorMessage = "{0} is required")]
        public string GroupCode { get; set; }

        [DisplayName("Group Name")]
        [MaxLength(20, ErrorMessage = "Group Code maximum length is {0}")]
        [Required(AllowEmptyStrings = false, ErrorMessage = "{0} is required")]
        public string GroupName { get; set; }

        public virtual List<User> Users { get; set; }
    }

用户类：

[Table("tblUser")]
public class User : MyTemplate
{
    public User()
    {
        UserGroup = new UserGroup();
    }

    [Key]
    [Required(AllowEmptyStrings = false, ErrorMessage = "User ID is required and use for login.")]
    [DisplayName("User ID"), Column("UserID", TypeName = "varchar")]
    [MaxLength(15, ErrorMessage = "User ID maximum length is 15 characters.")]
    public string UserID { get; set; }

    [Required(AllowEmptyStrings = false, ErrorMessage = "User name is required")]
    [MaxLength(20, ErrorMessage = "User name maximum length is 20 charachters")]
    [DisplayName("User Name"), Column("UserName", TypeName = "varchar")]
    public string UserName { get; set; }

    [DisplayName("Email"), Column("Email", TypeName = "varchar")]
    [DataType(DataType.EmailAddress)]
    [MaxLength(128, ErrorMessage = "Email address maximum length is 128 charachters")]
    [Required(AllowEmptyStrings = false, ErrorMessage = "Email address is required.")]
    public string Email { get; set; }

    [DisplayName("Password"), Column("Password", TypeName = "varchar")]
    [DataType(DataType.Password)]
    [Required(AllowEmptyStrings = false, ErrorMessage = "Password is required.")]
    [MaxLength(128)]
    [MinLength(6, ErrorMessage = ("Password at least 6 charachters."))]
    public string Password { get; set; }

    [DisplayName("User Group"), Column("GroupCode", TypeName="varchar")]
    [Required(AllowEmptyStrings = false, ErrorMessage = "User group is required")]
    [MaxLength(20, ErrorMessage = "Group code maximum length is 20 charachters")]
    [ForeignKey("UserGroup")]
    public string GroupCode { get; set; }

    [DisplayName("Status"), Column("Status", TypeName = "tinyint")]
    [Required(AllowEmptyStrings = false, ErrorMessage = "User status is required")]
    public UserStatus Status { get; set; }

    [DisplayName("Roles"), Column("Roles", TypeName = "varchar")]
    [MaxLength(32)]
    [Required(AllowEmptyStrings = false, ErrorMessage = "Roles is required.")]
    public string Roles { get; set; }

    public virtual UserGroup UserGroup { get; set; }
}

这是我的用户背景：

public class UserDBContext : DbContext
    {
        public UserDBContext() : base("DConn")
        {
            Database.SetInitializer<UserDBContext>(new CreateDatabaseIfNotExists<UserDBContext>());

        }

        public DbSet<User> Users { get; set; }
        public DbSet<UserGroup> UserGroups { get; set; }
    }

如果我在GroupCode或UserGroup属性中添加外键，则不会创建数据库表（tblUser）。我搜索了许多解决方案而没有运气。我尝试使用流畅的API并遇到同样的问题。有人可以帮帮我吗？